1. Field of the Invention
The present invention relates generally to the interconnection of the audio and video data streams associated with multiple media devices. More particularly, it relates to a system and method for interconnecting multiple audio and video sources to multiple audio and video destinations concurrently, under computer control, and synchronously. The invention further allows for dynamic reconfiguration, synchronously concurrent with an external or internal timing pulse, especially for multi-media program creation and presentation, in tandem with a host computer. Further, the invention embodies a software driver, resident in the host computer, that facilitates a friendly user interface ideally suited for graphical control of the subject invention's functions.
2. Description of the Prior Art
Prior teachings generally deal with the interconnection of multiple media devices to a single destination, as would be the case in a conventional editing environment. For example, the following issued U.S. Patents disclose examples of such systems:
U.S. Pat. No. 4,502,026, issued Feb. 26, 1985 to Imazeki et al. describes a method of switching RF signals containing modulated video information from several sources to two possible destinations. Source to destination coupling is accomplished through a coupling transformer (balun coil) that serves to provide the necessary DC isolation and present the signal to the destination device as a balanced line.
The isolation method shows the importance of managing impedances when coupling a single source to two destinations. Switching is accomplished mechanically through slide switches, and because the information (video data) is modulated onto an RF carrier while being switched, there is minimal corruption of the video signal after it is extracted from the RF carrier.
U.S. Pat. No. 4,495,497, issued Jan. 22, 1985 to Molnar teaches a method of controlling the switching function associated with a data transmission path remotely through excitation and sense lines. Although the patent does not address video and audio data connectivity specifically, the data transmission lines and control signals are digital, and thus could be used for the routing of media video and audio information when digitally encoded.
The communications paths are treated as transmission lines, and as such, one would presume information could be routed over long distances. Molnar's treatment of transmission lines shows the need for careful impedance control and buffering to avoid signal distortion, or data errors.
U.S. Pat. No. 4,581,644, issued Apr. 8, 1986 to Deiss teaches a method of routing video between a monitor, auxiliary video source, and a video tape recorder (VTR). The bus is a single video channel with the necessary control logic to assure that the video signal is always terminated to prevent ghosting.
U.S. Pat. No. 4,647,973, issued Mar. 3, 1987 to Deiss teaches a switch method that assures that the video path is always terminated with a suitable impedance. This teaching is closely tied to U.S. Pat. No. 4,581,644, and is a refinement of the switching technique described therein. In both of these teachings, the switches are located in close proximity to the peripheral device to which it is connecting. This method requires that the video path be treated as a transmission line, and impedance matching becomes critical.
U.S. Pat. No. 4,746,982, issued May 24, 1988 to Seen teaches that a video bus can be used in such a way as to allow multiple destinations to be connected to a bus driven by one source. The specific implementation requires two video paths, one to provide the input path to a cross-over switch, and the other connected to the output of the cross-over switch to connect to several video destinations.
The cross-over switch is equipped with the necessary buffering to drive the video signal out the second video path. It is the second video path that can be connected to multiple device inputs.
The specific implementation described shows color video separated into its color components, RGB and Sync, for purposes of interconnecting on the video bus. Although RGBS separation has advantages when the video signal is being modified or otherwise adjusted, it is generally difficult to maintain correct color balance with total luminance because the three video paths (RGB) must be identical.